Legacy systems may appear stable, but they steadily increase costs and operational risk across the organisation. This article examines how outdated IT infrastructure leads to rising maintenance efforts, dependency on scarce expertise, security vulnerabilities and growing compliance challenges. It explains how legacy applications limit scalability, slow down innovation and reduce overall productivity. The article also highlights the hidden impact on business agility, as ageing systems make integration and modernisation increasingly complex. By understanding these often-overlooked expenses, organisations can make informed decisions about archiving, modernising or decommissioning legacy systems to reduce long-term costs, minimise risk and create a more efficient, future-proof IT landscape.